The invention relates to a visual lamination for the purpose of finishing the surface of printed and other products by applying laminating films by means of a 100% adhesive system, for which the adhesive-coated laminating film is laminated with a heated laminating roller onto the product, as well as to an apparatus for producing such a visual coating.
A plurality of different systems for applying a visual lamination, which have more or less gained acceptance in practice, are already known. Aside from the use of solvent-containing film laminating adhesives, for which the adhesive is applied on the laminating film or on the product to be laminated by means of a dipping roller with a doctor blade system, dispersion film-laminating adhesives, which are likewise processed wet, have also already been used. Both systems have no or, at best, limited prospects in the future, since solvent-containing adhesives will be banned completely in the foreseeable future for environmental reasons and dispersion film-laminating adhesives, although they comply with the waste air regulations of the EU, nevertheless have the disadvantage that they require higher amounts to be applied, that certain processing problems arise, that there are difficulties with printing certain materials and that, aside from a higher energy consumption, particularly longer cleaning times are required in order to prepare a laminating machine for use once again after it has been stopped.
Furthermore, so-called solventless film laminating adhesives have also already been used, mostly in the form of liquid polyurethanes, which are activated by moisture from the air or from the material being printed. Further processing directly subsequently is not possible, since the reaction between the adhesive and the moisture is not concluded immediately after the laminating process. However, because of the isocyanates they contain, such adhesives are harmful to the environment and the products treated therewith must be disposed of as hazardous waste. Furthermore, the adhesive, after being activated by moisture from air, always becomes a solid, so that an increased cleaning expenditure becomes necessary. The advantage of such solventless film laminating adhesives, namely that the adhesive is a 100% system, that is, that no solvents, in addition to the original adhesive, are used and only a small amount needs to be applied and that furthermore a high gloss can be achieved, cannot be utilized satisfactorily because of the disadvantages.
Correspondingly the same also applies to the UV-curing film-laminating adhesives, which once again are 100% systems. Such UV-curing adhesives can be processed with the application of small amounts and without losses and make high belt speeds possible. However, UV-processing machines must be cleaned very carefully and provided with protective devices, which are opaque to UV light, since remaining residues of adhesive could otherwise polymerize fully and thus lead to protracted cleaning of parts of the equipment. It is, however, a disadvantage of such UV-curing adhesives for visual laminations with the help of laminating films that, on the one hand, they are not permitted for primary food packages, that there is always a certain, residual odor, which is very disturbing or totally impermissible in many cases, that there are problems with certain printed goods and that more controls are required (UV radiator, curing, printed goods, etc.).
A laminating system, which is used particularly frequently, is one for which thermofilms are employed for the lamination. In this case, the films are provided with an adhesive coating already by the manufacturer. It is merely necessary to bring together the coated films with the printed material to be laminated or the like, in order to attain the lamination with a heated calender roller. This means that the necessary investment in machinery is small and that it is necessary to store, dispose of or apply the adhesive. As a result, the preparation times are shorter, the cleaning problems are less and the laminated products can be processed further immediately.
The disadvantage of such thermofilm lamination consists of having to keep stocks of several types of film in all widths, poor heat stability and tear-off difficulties. Aside from edge-trimmings waste, which causes appreciable costs because of the expensive thermofilms, there is the difficulty that, when the paper is laid flat, the paper material must be broken over a knife, as a result of which problems arise with the reverse side. Furthermore, with many film rolls, a fold is formed at the edges and it has so far been impossible to eliminate the cause of this fold. Finally, the very high price is a particular disadvantage.